1. Field of the Invention
The present invention relates to a further improvement in a focusing system of a camera, particularly a camera having a device to automatically detect an in focus position of a photo-taking optical system.
2. Description of the Prior Art
Such a camera having a so-called automatic focus detecting device for automatically detecting a focusing condition of a photo-taking optical system in place of a human eye, in which further a setting of the photo-taking optical system is automatically done together with an automatic operation of focus detection, has been proposed hereto in many ways and has been actually employed in some cases.
While a majority of such camera uses a motor as a driving source for automatic setting of a photo-taking optical system, when a motor is used as a driving source as mentioned, there are such shortcomings that a reduction device and a large capacity power source, etc. therefor are needed together with said motor, which hinders reduction in a size and a weight of camera also a reduction in cost of the same, further when a servo-motor, etc. is used for automatically adjusting the photo-taking optical system to a proper direction with such information as a direction to which focusing is deflected either to a foreground or to a background being taken into consideration, a control circuit thereof becomes complicated and along therewith a control of said motor with a high degree of accuracy becomes difficult, thus exact focusing of the photo-taking optical system becomes very difficult.
In view of said disadvantages in using such motor, there is a system which uses a driving mechanism employing a functioning power of a spring in place of a motor as the above mentioned driving source, but even in said case there are such disadvantages that such complicated mechanisms as a speed regulating mechanism and a stopping mechanism, etc. are needed, also it is necessary to reset the photo-taking optical system always at a prescribed initiating position together with an adjusting mechanism thereof, thus a mechanism for that end needs to be provided, also its handling becomes very troublesome, further, it becomes difficult to stop and retain the photo-taking optical system quickly in response to an in focus signal outputted from a focus detecting device only by a simple mechanism, thus exact setting of the photo-taking optical system can not be done.
Also, when the focus adjusting of the photo-taking optical system is automatized, a manual adjusting thereof becomes impossible in an ordinary case, therefore, there will be great inconveniences in such case when for example, a photographer wants to take a picture of the entire zone of the scene with a deepened depth of field.
On the other hand, when an automatization is done only for focus detection and automatization of the adjusting of the photo-taking optical system is not intended, the above mentioned disadvantages can be eliminated, however, many of such systems have an in focus information from a detecting device indicated by such indication means as a meter, a lamp, etc., and in such set up, a camera user is required to have certain skill in adjusting the photo-taking optical system for finding out an in focus position thereof, also it is either very difficult or totally impossible to detect the directivity of deflection of focusing in the photo-taking optical system only by such indication means as a meter or a lamp, etc., thus the camera user is compelled to make such very troublesome handling that it is judged whether or not the photo-taking optical system reaches the in focus point by the indication state of the indication means at a time when the photo-taking optical system is shifted back and forth near the in focus point, thus it is very inconvenient to achieve exact focus adjusting of the photo-taking optical system.